tile: optimize strnlen using SIMD instructions
Using strlen as a model, add length checking to create strnlen.
Signed-off-by: Ken Steele <ken@tilera.com>
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
diff --git a/arch/tile/lib/strnlen_64.c b/arch/tile/lib/strnlen_64.c
new file mode 100644
index 0000000..2e8de6a
--- /dev/null
+++ b/arch/tile/lib/strnlen_64.c
@@ -0,0 +1,48 @@
+/*
+ * Copyright 2013 Tilera Corporation. All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, version 2.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT. See the GNU General Public License for
+ * more details.
+ */
+
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/module.h>
+#include "string-endian.h"
+
+size_t strnlen(const char *s, size_t count)
+{
+ /* Get an aligned pointer. */
+ const uintptr_t s_int = (uintptr_t) s;
+ const uint64_t *p = (const uint64_t *)(s_int & -8);
+ size_t bytes_read = sizeof(*p) - (s_int & (sizeof(*p) - 1));
+ size_t len;
+ uint64_t v, bits;
+
+ /* Avoid page fault risk by not reading any bytes when count is 0. */
+ if (count == 0)
+ return 0;
+
+ /* Read and MASK the first word. */
+ v = *p | MASK(s_int);
+
+ while ((bits = __insn_v1cmpeqi(v, 0)) == 0) {
+ if (bytes_read >= count) {
+ /* Read COUNT bytes and didn't find the terminator. */
+ return count;
+ }
+ v = *++p;
+ bytes_read += sizeof(v);
+ }
+
+ len = ((const char *) p) + (CFZ(bits) >> 3) - s;
+ return (len < count ? len : count);
+}
+EXPORT_SYMBOL(strnlen);